Do you ever wonder how the outdoor lights of commercial spaces or a dark street turn on all at once? Most likely, they were automated with photocells.
Photocell or photo control has the potential to make your life easier when they are integrated with smart lights. Then you will not have to worry about extra energy consumption at all! These photocells will automatically turn lights on or off depending on the available ambient light. Besides, this accessory can be used in mood lighting, intruder alarms, and automatic doors to serve you with maximum convenience.
So, keep reading and find out some top conversion options to find the right photocell for your setup.
What Is A Photocell?
A photocell is a small, low-power, and easy-to-use light-sensitive module. It is a sensor that changes the resistance of an electrical circuit based on the amount of light present in the surroundings. Thus, it helps control smart lights and other devices automatically. In addition, it comes in different shapes and sizes to be used for various light fixtures.
What Is The Photocell Made Of?
Semiconductor Material
The semiconductor material is the main component of a photocell. The mechanism of a photocell depends on the type of semiconductor material that changes electrical resistance in response to light intensity.
Cadmium Sulfide (CdS) is most commonly used in photocells. As a matter of fact, photocells are sometimes called CdS cells. It is sensitive to visible light and costs relatively less. Apart from that, Cadmium Selenide (CdSe), Silicon (Si), Germanium (Ge), and Cesium (Cs) are used for specialized applications.
Encapsulation
A housing or casing is used to encapsulate the sensitive semiconductor material from harsh environmental factors. This encapsulation increases the lifespan and performance of the photocell.
Electrodes
Two electrodes are connected to the semiconductor that facilitates the flow of current when exposed to light. One electrode is made of conductive materials like metals, and the other is made of transparent conductors like Indium Tin Oxide (ITO).
Connection Leads
There are wires called connection leads attached to the electrodes. As its name suggests, it creates a connection between the photocell and the lighting system. An electrical signal is transmitted through these leads.
Protective Coating
Sometimes, a protective coating over the semiconductor material is given for extra protection. It shields the semiconductor from external factors and increases its durability.
Housing
Housing is the sturdy casing or enclosure where the photocell remains. It is necessary for easily installing and mounting the photocell in lighting fixtures and control systems.
Optical Filter (Optional)
In some cases, an optical filter is used in the photocell to limit the wavelengths of light that can reach the semiconductor. It controls the photocell’s response to specific light sources or ambient conditions.
How Does A Photocell Work?
A photocell or light sensor imitates the working principle of the photoelectric effect described by Albert Einstein in 1905. Here, the photocell uses a light-dependent resistor (LDR) that contains a semiconductor material. Normally, Cadmium Sulfide is used for this material.
When light hits the photocell, light energy excites the electrons to move and create an electric current. At the same time, the resistance of the photocell decreases, which allows more electron flow. This flow of electrons shuts the light off. The sensor can detect the level of light intensity. During the daytime, it will allow electron flow, and the light will be turned off.
When it is dark, the photocell’s resistance increases, the electric current stops, and the sensor turns the light on. This automatic operation provides an energy-efficient lighting control without any manual operation.
Types of Photocells
Based On The Industry Standard And Application
1. NEMA photocells
NEMA photocells stand for National Electrical Manufacturers Association photocells that come with wire-in photocontrol and twist-lock light control systems. More often, it is used for basic switching on and off of lights. The 3-pin, 5-pin, and 7-pin NEMA sockets are commonly used for streetlights or floodlights. However, it has limited functionality in terms of compatibility with smart lights.
2. Zhaga photocells
Zhaga photocells consist of a Zhaga socket and a sensor. Also, it is used for modern and smart LED lighting systems. It is flexible and allows various functions such as dimming, sensor integration, advanced control, etc. Moreover, no wiring is required while installing this photocell.
Based On the Operating Principle
1. Photoconductive Cells
This electrical device works as a light-sensitive resistor. It is also known as a light-dependent resistor (LDR) or photoresistor. This semiconductor device changes electrical resistance according to changes in light intensity. With more light on the cell, the resistance decreases, and more current flows. In contrast, the resistance increases in the presence of low light and less current flows.
2. Photovoltaic Cells
The photovoltaic cells transform solar energy into electrical energy. To elaborate, the semiconductor material of the cells absorbs the photons of the sunlight and generates a flow of electrons. As a result, an electric current is created, which is known as solar electricity.
3. Photoemissive Cells
Photoemissive cells are known as phototubes, which follow the mechanism of the photoelectric effect. In addition, the material of this cell emits electrons when energy is supplied to the material. First, the electrons within the material become excited and jump to higher orbits. After that, it releases energy and comes to the original orbits.
4. Golay Cells
Golay cells function by sensing Infrared radiation. For instance, a blackened metal plate cylinder is filled with xenon gas on one end. After that, IR energy falls on the blackened plate and heats the gas. Heated gas bends the flexible diaphragm at the other end of the cylinder. This motion then regulates the output energy level.
5. Charge-Coupled Devices (CCDs)
Charge-coupled devices have maximum accuracy compared to other photocells. When an object reflects photons, this device captures them and breaks down the image into pixels.
6. Photomultiplier
It is a very sensitive type of detector. This photomultiplier can multiply unclear light by 100 million times.
Based On Output Type
1. Analog Photocells
Analog photocells generate a continuous voltage or current that changes proportionally to the amount of light detected. These photocells offer accurate measurement of light intensity. So, it is used in cameras and scientific instruments to control exposure time and light levels. A photoresistor is an example of an analog photocell.
2. Digital Photocells
Digital photocells normally generate a binary output based on the set threshold of light. It is used in switching tasks that turn on or off lights when the light level drops below a particular level. Also, automated street lights and alarms use this photocell.
Applications Of Photocells
Outdoor Lighting
Photocells are commonly used to control outdoor lights of the garden, patio, driveway, passage, doorway, etc. Using photocells in these areas will increase visibility and security automatically according to the ambient lighting level.
Street lighting
Photocells used in streetlights contribute to less energy consumption. For example, they turn the lights on at dusk and off at dawn without any manual operation.
Indoor lighting
You can integrate the photocells into the indoor lighting system to automatically adjust the brightness level.
Security Systems
Photocells are also applied in different security systems, like burglar alarms, to trigger the alarm by detecting interruptions in a beam of light. Apart from that, it is used to monitor access to rooms or buildings. It records the entry and exit events of the place when the light beams are interrupted.
Automatic Doors
Another wide use of photocells is automating door opening and closing with them. When the light beam gets interrupted, a circuit opens, and a relay activates. This event provides enough power to open or close the door automatically. In other words, photocells of the automatic doors ensure hands-free operations.
Camera Control
Photocells in exposure meters are used with cameras for better photography. It helps to know the correct time of exposure to get a good photo.
Light Meters
Photocells present in light meters measure light intensity. Here, the photocells work as sensors that convert light intensity into electrical signals. After that, this signal helps control the lighting systems automatically.
Timers
Using photocells within timers, the timing and speed of racers are calculated in races.
How Can a Photocell Be Bypassed?
If you want to keep your light on constantly or control it through the existing switch or timer, bypass the photocell using the following methods.
Method 1: Using A Shorting Cap
When the photocells are externally mounted through twist-lock sockets or adapters, replace the photocell with a shorting cap. Then you can set the light in an always-on state mode while keeping the circuit of the LED light fixture closed. Also, you will be able to control the lights externally with a central photocell or switch system.
Method 2: Utilizing DIP Switch or Slide Switch
You will find a DIP switch or slide switch in canopy lights and dusk-to-dawn barn lights. Using these, you will turn the photocell sensor on or off according to your requirements. As a matter of fact, no rewiring or replacing of any component is needed in this method.
Method 3: Disconnecting the Wiring
Photocells found in wall packs are easily bypassed by disconnecting the wiring. So, unplug the photocell and control the lights as you want.
Method 4: Covering the Sensor Temporarily
Instead of permanent bypassing, you can temporarily bypass the photocell by covering the sensor. First, find the small round or square black sensor on the light fixture. Then use a black electrical tape or a thick cloth to cover it. In this way, the sensor will think it is night, and the lights will turn on.
How To Choose The Right Photocell?
Mounting Types
While choosing the photocell, you need to consider how it will be mounted. For example, the type of photocell will vary depending on its mounting position on a pole, wall, or within a fixture. So, choose the compatible photocell based on the mounting location.
Lighting Type
The design of the photocell changes based on the bulb types. So, think of what type of light you are working with, for example, LED, incandescent, or others, before selecting the photocell.
Spectral Response
Each photocell has a specific photoconductor material with its unique spectral response. That is why the spectral response must be considered while selecting a photocell for a specific application.
Compatibility And Voltage Requirements
You need to make sure that the photocells are compatible with your existing lighting system before buying them. For example, ensure your photocell fulfills the voltage requirements of your system to avoid damage or malfunction.
Environmental Ratings
There are Ultraviolet (UV) resistance ratings and Ingress Protection (IP) ratings under the category of environmental ratings for photocells. First, the IP ratings refer to what extent a photocell is protected against dust and water. It consists of two digits, where the first digit determines protection against solids like dust, debris, etc. In addition, the second digit denotes protection against liquids like water. The bigger the rating, the higher the level of protection. For instance, an IP65 rating means that a photocell is protected against dust and low-pressure water jets from any direction. Moreover, an IP67 rating means it is protected against dust and immersion in water for up to 30 minutes.
Secondly, UV resistance ratings mean whether the photocells can withstand ultraviolet light exposure in an outdoor area. Photocells with adequate UV resistance can tolerate prolonged exposure to sunlight without degradation of performance.
Price and Cost-Benefit Analysis
You have to consider the initial purchase price and other long-term costs associated with photocells, including maintenance costs, potential replacement costs, etc. Then determine if this amount of cost is worth it for the value and benefits provided by it.
Packaging
Different types of coatings, such as glass, metal, or plastic coatings, are used in photocell packaging. Consider the pros and cons of all packaging types and select the right one for you. For example, choose a metal coating to get maximum protection. Alternatively, if you have a limited budget and need photocells for street lighting, then go for a plastic coating.
Temperature Range
The photoconductive materials operate better within the temperature range of –40°C to 75°C. So, consider the temperature of the location before buying the photocells.
How to Install a Photocell?
Here is the professional guide on how you can install a photocell easily and safely:
Step 01: Selection Of The Photocell Installation Location
Photocells are installed in different locations for different purposes. For example, wall-mounted photocells are installed for outdoor lighting, ceiling-mounted photocells are for indoor areas, and pole-mounted photocells are for streetlights. So, deciding on the location for photocell installation is your first task. Also, make sure that the location is not exposed to extreme temperatures, moisture, or direct sunlight.
Step 02: Choosing The Height and Angle For Installation
Choose the appropriate height and angle for photocell installation. Generally, 6-8 feet is recommended for photocell mounting. In addition, the angle of the photocell should align with the area that needs illumination.
Step 03: Turning Off The Circuit Breaker
Now, turn off the circuit breaker to shut down the power source of your lighting system.
Step 04: Disassembling The Housing Containing The Lights
At this moment, take apart the components of the housing that hold the lights. Also, disconnect the black wire that connects the house and the light fixture.
Step 05: Connecting The Photocell
There are two black wires on the photocells. Now connect one of those wires to the black wires coming from the building. Twist the exposed copper wire to ensure a tight connection. After that, connect the second wire of the photocell with the black wire of the light fixture.
Step 06: Covering The New Connections
Now use electrical caps to cover the new connections. To be safe, ensure that there is no exposed copper wire. Then test the photocell by turning on the power back at the breaker. Use your hands to cover the photocell. If the lights turn on, then it is working right. Finally, finish the work by putting the light fixture back together.
Maintenance Tips For Photocells
Regular Cleaning
You need to clean the surface of the photocell with a soft, dry fabric to remove superficial dirt. Do not use harsh chemicals that can damage the sensor.
Removing Obstructions
Check if there are any physical objects obstructing the photocell. Remove it to ensure full functionality of the photocell to detect light.
Checking Electrical Connections
Inspect if all the electrical connections are secure and free from corrosion. Fix the loose connections immediately to prevent further damage.
Ensuring Proper Alignment
If your lighting system has separate transmitter and receiver units, align them properly for better performance of the photocell.
Common Problems and Troubleshooting Tips
Don’t worry if you face issues with your photocell. Just go through the troubleshooting tips below and get an instant solution!
Problem 01: Lights Not Turning On Or Off
Solution: First, check if anything is blocking the photocell’s view of the light source. Remove the obstruction and check again. Furthermore, use a multimeter to ensure the wiring connections are secure. Apart from that, check for cracks or water damage. In case of severe damage, replacement may be necessary.
Problem 02: Flickering Lights
Solution: Inspect for loose or incorrect wiring and fix it accordingly. In addition, make sure that the photocell is not sensing light from other sources. Also, for areas with fluctuating light, use a photocell with a built-in delay.
Problem 03: Photocells Not Responding To Light Changes
Solution: Adjust the sensitivity settings of the photocells according to the environment. Also, avoid pointing it directly at the light it’s controlling while installing.
Problem 04. Excessive Clicking Noise
Solution: If your photocell is making an excessive clicking noise, see if there is any internal failure and fix it accordingly. In addition, securing the power supply and the connected load can solve this problem.
Problem 05: Lights Turning On At The Wrong Time
Solution: Avoid direct artificial light while installing the photocell. It is only supposed to be exposed to reflected light. So, choose a place that is shielded from direct light sources.
FAQs
The Bottom Line
Photocells are a crucial addition to the automated lighting system of a place. It is also suitable for both indoor and outdoor use. Now that you have come to know the perks of using photocells in smart LED lights, choose LED lighting options, starting from modern linear bars, LED strips, to LED Neon Flex from LEDYi Lighting.
Besides, you will get the desired products according to your needs, along with various customization options. Moreover, we offer you 3 to 5 years of warranty on our fixtures. So, contact us ASAP to place your order!
